Field of the Invention
The present invention generally relates to an image sensor and manufacturing method thereof. More particularly, the present invention relates to an image sensor in which the strength of adhesion between a photoconductive layer and a substrate is increased.
Description of the Related Art
Conventionally, X-rays for medical or industrial applications have typically used films and screens. In this case, the use of resources and time becomes inefficient due to problems related to the development and storage of the taken films.
Hence, digital-type image sensors are currently widely used. Such image sensors are classified into: indirect conversion-type image sensors and direct conversion-type image sensors.
In indirect conversion-type image sensors, X-rays are converted into visible light using a scintillator, after which the visible light is converted into an electrical signal. By comparison, in direct conversion-type image sensors, X-rays are directly converted into an electrical signal using a photoconductive layer. Direct conversion-type image sensors are suitable for use in high-resolution systems because there is no need for an additional scintillator and the spreading of light does not occur.
A photoconductive layer used for the direct conversion-type image sensors is formed on a complementary metal-oxide semiconductor (CMOS) substrate or a thin film transistor (TFT) substrate by performing vacuum evaporation on a surface thereof. A specific high process temperature is required for forming the photoconductive layer to perform vacuum evaporation. Herein, thermal stress occurs between the substrate and the photoconductive layer, and thus delamination or cracking of the photoconductive layer may occur since adhesion between the substrate and the photoconductive layer is degraded by the thermal stress.
Accordingly, reliability of image sensors is deteriorated since current leakage increases due to the delamination or the cracking of the photoconductive layer and thus charge collection efficiency is degraded.
The foregoing is intended merely to aid in the understanding of the background of the present invention, and is not intended to mean that the present invention falls within the purview of the related art that is already known to those skilled in the art.